Three Finnish incontinentia pigmenti (IP) families with recombinations with the IP loci at Xq28 and Xp11.

The locus (IP2) for the hereditary form of incontinentia pigmenti (IP) has been mapped to Xq28 by linkage analysis. We studied three IP families with polymorphic markers in the Xq28 region. In two families we observed recombination between the marker loci and IP. In the third family no crossing overs were seen and linkage to the Xq28 region could not be excluded. The other IP locus (IP1) has been mapped to Xp11.21, because of sporadic cases of IP with X-chromosomal alterations involving Xp11.21. To check whether this locus is linked to IP in these families, we used polymorphic markers in the Xp11 region. In all three families recombinations were observed, thus excluding linkage to this locus in these IP families.